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HSCI Objectives To learn the basic anatomy and physiology of the heart –Muscle/ pump To understand the mechanism for the delivery of oxygen and nutrients to the organs and tissues of the body To become familiar with mechanisms to control blood pressure To understand the process of atheroma formation (Next Class)

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HSCI The Need for Circulation All living cells require metabolic substrates (e.g. oxygen, glucose, amino acids) and a mechanism to remove the byproducts of metabolism (e.g. carbon dioxide, lactic acid- stuff we need to remove) In human beings most cells are not in contact with the external environment The ultimate purpose of the cardiovascular system is to facilitate exchange of gases, fluid, electrolytes, large molecules and heat between cells and the outside environment The heart and vasculature ensure that adequate blood flow is delivered to organs so that this exchange can take place. Klabunde, RE Cardiovascular Physiology Concepts Lippincott, Williams and Wilkins, 2005

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HSCI Cardiac Cycle Rhythmic contraction of the heart relies on the organized propagation of electrical impulses along its conduction pathway. The electrical impulse spreads along each cardiac cell and rapidly between neighbouring cells Electrical action potential leads to physical contraction of the cardiac muscle cells

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HSCI Heart Sounds First Heart Sound: –Closing of mitral and tricuspid valves and contraction of the Ventricles Second Heart sound: –Closure of the Aortic and Pulmonary valves Systole: (Contraction) –The time between the 2 heart sounds Diastole: (Relaxation) –The time between the second heart sound and the first

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HSCI Summary 3 … then primary care assessment History – The story  Pain on exertion or at rest  Shortness of breath, etc. Look – diagnosis  Edema – swelling – blood flow doesn’t get pumped back Listen  The heart sounds  Blood pressure – resistance in the distribution system Feel  The pulses ECG  Assess the electrical conductivity & efficiency of heart cycle THESE ARE THE BASIC TOOLS FOR THE GPs Obviously more sophisticated methods are needed/available for further investigation

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HSCI Blood Pressure

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HSCI Objectives Review of structure & function Learn the role of various blood vessels in oxygen and nutrient supply and removal Blood Pressure and its determinants Understand how different factors might influence blood pressure levels Become familiar with mechanisms of controlling blood pressure Learn how blood pressure is measured Hypertension or High blood pressure Impact of hypertension

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HSCI Homeostatic Regulation: Baroreceptors Carotid arteries (on the way to the brain) Aortic arch (on the way to the heart)  Sensitive to distension of the vessel  Send message to medulla  Adjust sympathetic and parasympathetic activity

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HSCI BP Regulation – Orthostatic Hypotension heart isn’t adjusting but the pressure is high so you get dizzy

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HSCI Blood pressure Measurement Use Sphygmomanometer  1. Stop the blood flow  2. Release pressure gradually The first sound we hear will be the highest pressure = systolic  3. When there is no sound the ventricles are relaxed. There is still pressure in the arteries = diastolic

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HSCI HSCI Hypertension or High BP Hypertension refers to a blood pressure measurement of greater than 140/90 mm Hg (or on medication)  consistently, at rest Pre Hypertension Blood pressure is between 120/80 mmHg and 139/89 mmHg. You will see in manuals 90%: Unknown cause = Essential Hypertension. This is incorrect. Most can be attributed to some factor, usually overweight, high sodium intake, alcohol, physical inactivity, etc. Pathogenic process:  Vessels: Damages endothelial wall, promoting the formation of atherosclerotic plaques  Heart: Increases strain on the heart, leading to hypertrophy (pump is working harder), then back-up causing pulmonary edema, and then congestive heart failure

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HSCI Hypertension target in terms of definition Levels for defining hypertension have shifted down, from 165/95 mmHg to DBP >=90 mmHg to currently 140/90 mm Hg or on treatment Canadian recommendations include for diagnosis at different visits specific BP levels + presence of target organ damage or BP >=140/90 at visit 5 Epidemiologic diagnosis usually based on one or the mean of a few measures (2-6) >=140/90 Creates some difficulty for comparison of studies

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HSCI Global Prevalence of HBP Nearly 1 in 5 persons live with HBP i.e. Almost 1.5 billion people have hypertension in the world HBP = Silent killer - Symptoms are not overt & hence more people are UNAWARE In Canada about 19% of the adult population is hypertensive (approx. 4.6 million) (2009)

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HSCI The “Seventh Report of the Joint National Committee on Prevention, Detection, Evaluation, and Treatment of High Blood Pressure” (JNC VII) Provides a guideline for hypertension prevention and management. The following are the report’s key messages: In persons older than 50 years, systolic blood pressure greater than 140 mmHg is a much more important cardiovascular disease (CVD) risk factor than diastolic blood pressure. The risk of CVD beginning at 115/75 mmHg doubles with each increment of 20/10 mmHg; individuals who are normotensive at age 55 have a 90 percent lifetime risk for developing hypertension. HSCI

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HSCI JNC VII (Cont’d) Individuals with a systolic blood pressure of 120–139 mmHg or a diastolic blood pressure of 80–89 mmHg should be considered as prehypertensive and require health-promoting lifestyle modifications to prevent CVD. (High normal BP) Thiazide-type diuretics should be used in drug treatment for most patients with uncomplicated hypertension, either alone or combined with drugs from other classes. Certain high-risk conditions are compelling indications for the initial use of other antihypertensive drug classes (angiotensin converting enzyme inhibitors, angiotensin receptor blockers, beta-blockers, calcium channel blockers). HSCI

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HSCI JNC VII (Cont’d) Most patients with hypertension will require two or more antihypertensive medications to achieve goal blood pressure (<140/90 mmHg, or <130/80 mmHg for patients with diabetes or chronic kidney disease). If blood pressure is >20/10 mmHg above goal blood pressure, consideration should be given to initiating therapy with two agents, one of which usually should be a thiazide-type diuretic. The most effective therapy prescribed by the most careful clinician will control hypertension only if patients are motivated. Motivation improves when patients have positive experiences with, and trust in, the clinician. Empathy builds trust and is a potent motivator. HSCI

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HSCI How to measure BP at home Do not talk Keep back supported Place cuff mid-arm at heart level Be seated Ensure arm is supported Keep legs uncrossed Keep feet flat on the floor CHEP 2008

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HSCI It is estimated that in patients with stage 1 hypertension (SBP 140–159 mmHg and/or DBP 90–99 mmHg) and additional cardiovascular risk factors, achieving a sustained 12 mmHg reduction in SBP over 10 years will prevent 1 death for every 11 patients treated. In the added presence of CVD or target organ damage, only nine patients would require such BP reduction to prevent one death Ref: adapted from SHEP, SYST-EUR, STONE studies.